1. Field of Invention
This invention relates generally to pneumatic cushions or bolsters, and more particularly to a pneumatic bolster formed from an outer non-stretchable fabric casing enclosing an inflated rubber balloon imparting pneumatic properties to the bolster which renders it usable as a bumper for boats and the like, for protective packaging or for inclusion in wearing apparel.
2. Status of Prior Art
Pneumatic cushions are known which are formed of a heavy-duty bladder molded to assume a shape appropriate to its end use. When the bladder, whose stem is provided with a one-way valve, is inflated to an internal pressure sufficient to cause the bladder to assume its normal form, it will then have cushioning properties. Thus when a load is imposed on the pneumatic cushion, the air therein will be compressed and the cushion will yield to an extent that depends on the magnitude of the load.
A conventional pneumatic cushion formed by an inflatable bladder has two distinct drawbacks:
I. It is subject to rupture. Thus if a pneumatic cushion is placed on the flat seat of a chair and a heavy individual then sits on the cushion, the resultant increase in internal pressure will cause the sides of the bladder to bulge out. Should there be a weakness or defect in the bladder sides, such as a relatively thin region, the internal pressure exerted on this region may cause the bladder to burst.
II. Since a bladder is molded to assume a predetermined final form, when it is inflated by mouth to swell from its collapsed state to its final form, the degree of air pressure required for this purpose is low. Hence the internal pressure of the inflated bladder is low and it has relatively poor pneumatic properties, for the bladder offers little resistance to a load imposed thereon. In contradistinction, a rubber balloon in its molded form is much smaller than its inflated form, and it requires much more air pressure to inflate and stretch the rubber skin to cause the balloon to assume a desired final form which is not predetermined. Hence in an inflated rubber balloon, the internal air pressure is far greater than in an inflated bladder.
The play ball disclosed in my above-identified copending application exploits the high internal air pressure in an inflated rubber balloon, yet overcomes the inherent weakness of the balloon which is easily burst when subjected to external stress. To this end, the balloon is encased in a non-stretchable fabric casing shaped to assume the shape of a football or other play ball when fully expanded.
The fabric casing is provided with a closable port through which the balloon in its uninflated state is inserted, with its stem sticking out of the open port. Inflation of the balloon by mouth causes it to engage and conform to the inner surface of the casing, after which the stem is tied and pushed into the port. The port is then closed to fully encase the balloon, so that no portion thereof can be extruded from the casing.
As pointed out in my copending application, an un-encased rubber balloon has little strength; for by applying external pressure to one region thereof, the unstressed region is caused to stretch to its bursting point. But when the inflated balloon is fully encased in a non-stretchable fabric casing, even though the balloon, per se, is inherently weak, because of the casing does not permit any region of the balloon to further expand beyond its existing degree of expansion, the ball will not burst even if a heavy adult sits on the ball.
The reason the encased rubber balloon ball has high bounce characteristics is that its internal air pressure is much higher than, say, a conventional beach ball made of a non-stretchable plastic film. With a conventional beach ball, it takes little pressure to blow it up, for the plastic sphere offers little resistance to expansion until it is fully inflated, at which point since the material is non-stretchable, it cannot be further inflated. But with a stretchable rubber balloon, it takes much more air pressure to stretch the rubber from its initial state to its stretched and inflated state, as a consequence of which the internal air pressure is much higher than in a conventional beach ball.
While the present invention relates to a pneumatic bolster, not to a play ball, it exploits the strength and bounce characteristics of a play ball of the type disclosed in my copending patent application to provide a bolster having exceptional cushioning or protective characteristics.
Of prior art interest is the patent to Tillotson et al., U.S. Pat. No. 4,758,199, which discloses an imitation toy hot air balloon having a nylon outer envelope provided at its bottom with a circular opening to which a cylindrical skirt is attached, a gondola being suspended by wires from the skirt. Housed within the nylon envelope is an inflated latex balloon. But this balloon, whose function is to cause the envelope to assume its desired shape, is not fully enclosed by the envelope, and it is therefore not capable of withstanding heavy external pressures.